The breeding systems and floral visitors of two widespread African dry forest species of ethnobotanical significance

Forest products derived from woody trees, such as fruits, seeds, honey, wood and others, are important resources for supporting rural livelihoods. However, little is known about the breeding systems or floral visitors of trees that provide these resources, often due to the difficulty of accessing tree canopies. This study addresses key knowledge gaps from a data poor region, providing information on the breeding systems and contribution of biotic pollination to two trees abundant in south-central Africa, that provide forest product supports for rural livelihoods: Julbernardia paniculata (Benth.) Troupin and Syzygium guineense (Willd.) subsp. barotsense F. White (Fabaceae and Myrtaceae respectively). The breeding systems of these species were assessed by conducting controlled pollination experiments, and then measuring the effects on reproductive success to determine the degree of self-compatibility and pollen limitation. Floral visitors and their behaviour were observed to provide preliminary information on possible pollinator groups. S. guineense appeared to be self-compatible, while J. paniculata showed signs of both self-incompatibility and pollen limitation. Floral visitors of both species were dominated by bees, with native honeybees (Apis mellifera) providing the highest visitation rates. These insights provide the first steps for understanding the reproductive ecology of these key tree species and can help to inform sustained management and conservation aimed at protecting forests and supporting rural livelihoods, as well as broaden the understanding of the floral visitors, and contribution of biotic pollination to forest tree reproductive success.

Table S1: Reproductive strategies and floral visitors of studied species within the Fabaceae family.No information on pollination mechanisms or floral visitors was available for other species within the Africa-restricted Julbernardia genus, and so information from closely related species within the Fabaceae family within similar tropical habitats were included here.

Species
Current Subfamily

S1. Flower characteristics and floral visitors
Both S. guineense and J. paniculata have hermaphroditic flowers.J. paniculata has zygomorphic flowers with the stigma projecting at an angle beyond the eight to ten stamens and very small white petals mostly hidden within the brown velvety sepals which are retained during flowering;

S2. Breeding systems, visitation rates and behaviour
As well as the models testing the relationship between visitation rate and all the taxonomic groups observed, two alternative taxonomic groupings or subsets were tested using Kruskal Wallis tests: (a) one with all bee groups pooled and another with (b) bees kept split but all nonbee groups removed from the analysis with results as follows.

Syzygium guineense
Summary statistics of the breeding systems results are shown in Table S3.When bees were pooled into one taxonomic group there was still a significant difference in visitation rate among taxonomic groups (Kruskal Wallis: χ 2 = 175.68,p < 0.001, n=301, df=6): bees had significantly higher visitation rates than all other taxa, and Dipterans had higher visitation rates than ants, moths, Coleopterans, and butterflies.When only bee taxa were included in the analysis (as the visitation rates associated with non-bee taxa were comparatively very low), visitation rates were significantly different between bee groups: (Kruskal Wallis: χ 2 = 166.24,p < 0.001, n=258, df=5): honeybees (Apis mellifera) had higher visitation rates than all other bee groups, and Braunsapis bees had higher visitation rates than other bees except for honeybees.
Visitation rates associated with each of three behaviours (nectar foraging or N, pollen foraging or P, or both N+P) as well as the duration and frequency of each behaviour per taxon are visually depicted in Fig S3. to enable small values to be visible); and (c) the number of visits where each behaviour was observed, calculated as a percentage of the total observed visits (y-axis broken to enable small values to be visible).

Julbernardia paniculata
Summary statistics of the breeding systems results are shown in Table S4 and effect sizes for the J. paniculata fruiting success model in Table S5.
Table S4: Summary statistics for J. paniculata: the number of treated inflorescences, mean number of flowers treated per treatment, the total numbers of fruit and seed that were set per treatment and mean individual weights of these fruits and seeds per treatment in grams.When all bee taxonomic groups were pooled, visitation rates were still significantly different between taxonomic groups (Kruskal Wallis: χ 2 = 107.44,p < 0.001, n=240, df=5) with bees having significantly higher visitation rates than other taxa.When all non-bee taxa, which had much lower visitation rates than most bee groups, were removed from the analysis, and visitation rate was compared between bee groups, there was a significant difference between the visitation rates of the bee groups (Kruskal Wallis: χ 2 = 87.04,p < 0.001, n=240, df=5) with post-hoc tests showing that honey bees had significantly higher visitation rates than all other bee groups, and Meliponula had higher visitation rates than Hypotrigona, Amegilla, and Megachilidae.to enable small values to be visible); and (c) the number of visits where each behaviour was observed, calculated as a percentage of the total observed visits (y-axis broken to enable small values to be visible).
Fig S1: Images of S. guineense and some of the observed floral visitors.(a) S. guineense

Fig S3 :
Fig S3: Floral visitor behaviour of visitors to S. guineense flowers.Floral visitor behaviour of Visitation rates associated with each of three behaviours (nectar foraging or N, pollen foraging or P, or both N+P) as well as the duration and frequency of each behaviour per taxon are visually depicted in Fig S4.

Fig S4 :
Fig S4: Floral visitor behaviour of visitors to J. paniculata flowers.Floral visitor behaviour of

Table S3 :
Summary statistics for S. guineense: the total number of treated inflorescences per treatment, number of flowers treated per treatment, fruit and seed set per treatment and average weights of fruits and seeds per treatment.Inflorescence abbreviated as infl.

Table S5 : Proportion fruiting success per treatment for J. paniculata to support J. paniculata fruiting success model.
The total number of inflorescences per treatment that were